Nice DID method!
Feature request / question: Can a postcard be used rather than an envelope? i.e. in the Read operation, instead of the inner self-addressed envelope. (Probably not for the outer envelope, since it would then need to be reusable/returnable). Advantages: often cheaper postage, at least domestically; conserve envelopes, lower materials cost/complexity (simpler to manufacture a postcard than an envelope, no glue required); make use of postcards that might have nice pictures. Disadvantages: decreased privacy due to response being readable in transit (including the response signature); more susceptible to tampering or damage in-flight (including parts being covered by postmarks), inability to include attachments in the response other than stickers; may require more knowledge of the recipient's postal system (i.e. allowed dimensions for reduced postcard rate); simpler long-term storage.
Nice DID method! Feature request / question: Can a postcard be used rather than an envelope? i.e. in the Read operation, instead of the inner self-addressed envelope. (Probably not for the outer envelope, since it would then need to be reusable/returnable). Advantages: often cheaper postage, at least domestically; conserve envelopes, lower materials cost/complexity (simpler to manufacture a postcard than an envelope, no glue required); make use of postcards that might have nice pictures. Disadvantages: decreased privacy due to response being readable in transit (including the response signature); more susceptible to tampering or damage in-flight (including parts being covered by postmarks), inability to include attachments in the response other than stickers; may require more knowledge of the recipient's postal system (i.e. allowed dimensions for reduced postcard rate); simpler long-term storage.